Device-Free Passive Human Detection Using Wi-Fi Technology: Current State and Future Trend

Wireless LANs using Wi-Fi technology are now very common in indoor environments, making it unprecedentedly convenient and low-cost for users accessing digital services on the Internet. Wi-Fi signals are typically information carriers between a transmitter and a receiver, lots of signal features can be extracted from measurements of the transmitted signals to develop numerous innovative applications. Focusing on device-free passive detection using Wi-Fi technology, in this paper, we provide a review of existing works that were done for detecting human motion indoor by classifying these research efforts into three categories according to the used wireless signal features. Specifically, we first describe the Wi-Fi signal features that are frequently used for device-free detection of human mobility in indoor environments, including RSSI, CSI and TOF. We then separate existing work into three categories according to these wireless signal features. A set of potential applications that can be developed within this new open research area of device-free passive human mobility detection will be proposed. Finally, we will discuss existing research challenges and point out possible research directions.